I'm going with a t400 as well and I've been asking around about kickdown options too.I been hearing really good things about the kickdown unit that Lokar sells and I think that is the route I'm going.
Just another option for you.
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'72 C-10 Proud owner of a million new and used pieces that used to be and will once again be(god willing) a testament to the term "they don't build em like that anymore. 
'80 LWB 2wd beater
'67 GMC long fleet (cab donor)
'66 long step (parked till it's turn comes around)
'65 short step (parts truck that will donate it's bed and possibly frame to the '66)
'06 Grand Prix wife's car (she hardly lets me touch it)
my pics